1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
|
// Copyright (C) 2005 Nathaniel Smith <njs@pobox.com>
//
// This program is made available under the GNU GPL version 2.0 or
// greater. See the accompanying file COPYING for details.
//
// This program is distributed WITHOUT ANY WARRANTY; without even the
// implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
// PURPOSE.
#ifndef __PARALLEL_ITER_HH__
#define __PARALLEL_ITER_HH__
// An ugly, but handy, little helper class for doing parallel iteration
// over maps.
// Usage:
// parallel::iter<std::map<foo, bar> > i(left_map, right_map);
// while (i.next())
// switch (i.state())
// {
// case parallel::invalid:
// I(false);
// case parallel::in_left:
// // use left_value(), left_key(), left_data()
// break;
// case parallel::in_right:
// // use right_value(), right_key(), right_data()
// break;
// case parallel::in_both:
// // use left_value(), right_value(), left_key(), right_key(),
// // left_data(), right_data()
// break;
// }
//
// This code would make Alexander Stepanov cry; not only is it only defined
// for maps, but it will only work on maps that use the default (std::less)
// sort order.
#include "lexical_cast.hh"
#include "sanity.hh"
namespace parallel
{
typedef enum { in_left, in_right, in_both, invalid } state_t;
template <typename M>
class iter
{
public:
M const & left_map;
M const & right_map;
iter(M const & left_map, M const & right_map)
: left_map(left_map), right_map(right_map),
state_(invalid), started_(false), finished_(false)
{
}
bool next()
{
I(!finished_);
// update iterators past the last item returned
if (!started_)
{
left_ = left_map.begin();
right_ = right_map.begin();
started_ = true;
}
else
{
I(state_ != invalid);
if (state_ == in_left || state_ == in_both)
++left_;
if (state_ == in_right || state_ == in_both)
++right_;
}
// determine new state
I(started_);
if (left_ == left_map.end() && right_ == right_map.end())
{
finished_ = true;
state_ = invalid;
}
else if (left_ == left_map.end() && right_ != right_map.end())
state_ = in_right;
else if (left_ != left_map.end() && right_ == right_map.end())
state_ = in_left;
else
{
// Both iterators valid.
if (left_->first < right_->first)
state_ = in_left;
else if (right_->first < left_->first)
state_ = in_right;
else
{
I(left_->first == right_->first);
state_ = in_both;
}
}
return !finished_;
}
state_t state() const
{
return state_;
}
typename M::value_type const &
left_value()
{
I(state_ == in_left || state_ == in_both);
return *left_;
}
typename M::key_type const &
left_key()
{
return left_value().first;
}
typename M::value_type::second_type const &
left_data()
{
return left_value().second;
}
typename M::value_type const &
right_value()
{
I(state_ == in_right || state_ == in_both);
return *right_;
}
typename M::key_type const &
right_key()
{
return right_value().first;
}
typename M::value_type::second_type const &
right_data()
{
return right_value().second;
}
private:
state_t state_;
bool started_, finished_;
typename M::const_iterator left_;
typename M::const_iterator right_;
};
template <typename M> void
dump(iter<M> const & i, std::string & out)
{
out = boost::lexical_cast<std::string>(i.state());
switch (i.state())
{
case in_left: out += " in_left"; break;
case in_right: out += " in_right"; break;
case in_both: out += " in_both"; break;
case invalid: out += " invalid"; break;
}
out += "\n";
}
}
#endif
// Local Variables:
// mode: C++
// fill-column: 76
// c-file-style: "gnu"
// indent-tabs-mode: nil
// End:
// vim: et:sw=2:sts=2:ts=2:cino=>2s,{s,\:s,+s,t0,g0,^-2,e-2,n-2,p2s,(0,=s:
|
